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Visual impairment > Low vision 1 > Flashcards

Low vision 1 Flashcards

1
Q

why is VA important? (part 1 of 2- 6 reasons)

A
  1. Allows early eye disease detection
  2. Understand how much Mag we might need
  3. Social legal purposes : SI/SSI certification
  4. Predicating every day tasks
  5. compare the norm values
    6.Quantify patient’s subjective impression of visual performance
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2
Q

why is VA important? (part 2/2- 3 reasons)

A
  1. used to understand mag of required device can be
  2. Refraction procedures and decision
    making- eg when to dispense spx
  3. Predicting visual function for everyday tasks- eg LP- may struggle with daily activities vs px with 6/6
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3
Q

how do we note snellen notation?

A

VA = Test Distance/
Distance letter subtends 5 min of arc

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4
Q

which method of notation isnt used very much?

A

Keller A system

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5
Q

How is VA recorded?

A

Snellen and LogMAR

Example of converting:

6/60 - Snellen
60/6 - MAR
1 - log(MAR)
Keller A System 1 min arc MAR is A1 i.e. 6/6 is A1

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6
Q

what are the Most common charts?

A
  1. Snellen
  2. logMAR : bailt-lovie distance chart, ETDRS and keller A charts
  3. Thompson Test chart
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7
Q

Variables for an ideal chart?

A
  1. Portable
  2. Good Lighting
  3. High contrast
  4. Good range of sizes
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8
Q

What are the characteristics of Snellen chart?

A

It is cheap

However:
It is hard to control crowding (6/60 has no crowding)
Hard to score letter by letter

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9
Q

What are the characteristics of LogMAR ?

A

1.Equal number of letters on each line
2.Log progressive of letter size
3. Larger
4. More expensive

Each letter has a weight of 0.02

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10
Q

conversion factor of logMAR done at different distances?

A

-3m: Add 0.30
-1.5 m: Add 0.60
-0.75 m: Add 0.90
- 1m: Add 0.80
PRIYESH I DIDNT NUMBER SO NOONE GETS CONFUSED

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11
Q

Conversion factor for ETDRS test charts?

A

ETDRS similar but used at 4m, correction factor ½ distance- 2m-0,3, 1m= 0.6 0.5m= 0.9

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12
Q

what type of px do we used BRVT for?

A

Good for px HM, CF, where we can’t do letter VA- px with poor vision

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13
Q

how do we carry out BRVT - Berkeley Rudimentary vision test?

A

1.Tumbling E
2.Grating card pair : H or V. Used when Tumbling is not seen
3.Basic vision card :One area is white and one area is Black. Ask the px to point out which area is white and which is black

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14
Q

what is the Freiburg Visual acuity test and how does it compare with BRVT?

A

Similar to the BRVT but on the computer!

Landots C instead of tumbling E.
It does not have different ranges like BRVT does

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15
Q

How can we conduct home low vision testing and how do we do it?

A

1.)Home acuity Test
2.) Test carried out at 150cm/190cm (do 190cm if vision allows)- sent string of 150cm long- chart has 5 lines- ranges from 3/60 to 6/7.5 or if good va 190cmcm- 6/96 to 6/6
3.) Note correct answers

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16
Q

What is contrast threshold?

A

This is the smallest difference in luminance the px can detect.
We measure it using sine wave grating cards

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17
Q

What is contrast sensitivity?

A

The smallest difference in luminance that an observer can detect-is the reciprocal of the contrast threshold.

18
Q

how do we quantify CS?

A

values vary from 0 to 1
usually expressed as a percentage (0%-100%).

19
Q

How do we use contrast sensitivity?

A

We can plot the CS over a range of different frequencies

20
Q

Limitation of CSF?

A

Can’t measure VA

21
Q

How can we convert to cut-off frequency?

A

Divide 180 by the frequency and it will give the dominator for snellen

22
Q

What charts are used to measure contrast Sensitivity ?

A

Function acuity
Pelli-robson chart
Mars letter contrast test (in the pic)
Regan and baily -Lovie

23
Q

How does the functional acuity contrast test work?

A

1.The Spatial frequencies will change as you move along the letters
2.Contrast changes with numbers

24
Q

How does the Regan and Bailey -Lovie chart work?

A

Each chart will have different contrast.
10% contrast (Bailey-Lovie) and 96%, 50%, 25%, 11% and 4%(Regan)

25
Q

How does the Pelli-robson chart work?

A

The contrast changes every 3 Opto-type

It is scored like this :
If they get 2 then record that triplet
If doing LogMAR then add each letter
Done at 1M distance

26
Q

Why do we need to measure contrast?

A

1.Good VA and they have glare = low contrast sensitivity
2. Predict if aids will actually be useful or not
3. Binocular / Monocular vision

27
Q

on a Pelli Robson chart, what contrast level does VRS represent?

A

100%

28
Q

why is it important to measure CS? (7)

A
  1. Imp to assess LV px- eg cataract- can have 6/6- but contrast and glare problems
  2. px and everyday tasks
  3. Correlates better than VA with the performance on daily living tasks eg reading and mobility
  4. comparison to normal values
    5.Predict which patients will not benefit from optical aids.
  5. helps us see if electronic mag more ideal than hand mag
  6. helps determine to give MON or BIN LVA
29
Q

How is reading assessed?

A

Sentences rather then single letters.

30
Q

What is the point system in reading charts?

A

1/72 inchs
Example:
A ten point print will be 10/72 inch of a print

31
Q

what notation are reading charts given in and what distance are they used at?

A

sloan + 25cm

32
Q

What is the N - Notation system in reading charts?

A

the number will show the point size of the print

33
Q

what are MNREAD charts used for?

A

Used to measure (readign speed measure in words per min) and (reading acuity- measured in log)- logartihmic speed- correction factor needs to be applied

34
Q

why is it important to measure reading speed?

A

1.)reading plays a big role in ppls lives everyday
2.)Low vision has been classed involving reading at times-eg reading newspaper

35
Q

factors affecting reading ? (5 reasons)

A
  1. Acuity reserve (Print size relative to acuity threshold)
  2. Contrast reserve (Print contrast relative to contrast threshold )
  3. Field of view
  4. the number of simultaneously visible characters
  5. Central Scotoma- eg (advanced) ARMD
36
Q

methods to measure VF and give examples for each x

A

1.Gross VF (confrontation test)
2.Central fields: Amsler grid (more often used in clinic) or a tangent screen
3. Peripheral fields: arc perimeter
4.Scanning laser Ophthalmoscope -expensive- can visualise fixation though -usually 4 research
5. Microperimetry (Nidek MP1- this is good to compensate px poor fixation)

37
Q

what defects is the confrontation test good for detecting?

A

gross VF defects eg good for hemianopia (R or L etc)

38
Q

significance of measuring VF?

A

-Diagnostic importance
-Provide functional assessment of the extent, location and quality of areas of best vision
-Can help clinician determine what lva and rehab strategies the px might benefit from
-Provide info about how well an individual performs in real life conditions. - good if px needs guide dog etc- good for rehabilitation strategies

39
Q

methods to evaluate px BV (this shit wont leave us alone)

A

Cover Test
Stereopsis
Not routinely tested, but may give additional information
Titmus test - good if px has gross stereopsis can detect it
Frisby test - can adjust distance
TNO test
Stereo test- for spatial localisation- for judgement- check stereo acuity

40
Q

questionnaire LV px can fill in and give examples?

A

-QOL questionnaires assess functional capacity, social interactions and relationships, and wellbeing
-Low Vision Quality of Life Questionnaire (LVQOL)
National Eye Institute Visual Function Questionnaire (NEI- VFQ)

41
Q

do we really need QOL Questionnaires?

A

no, not if thorough H+S was done

42
Q

do the case study at end i am to lazy to include it x

A

dont ignore me go do it

Visual impairment (8 decks)

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